Silver halide emulsions



Patented Feb. 6, 1951 SILVER HALIDE EMULSIONS Walter Dewey Baldsiefen, Metuchen, N. J., assignorto E. I. du Pont de Nemours & Company, Wilmington, Del., a ccrporation of Delaware Serial No. 28,061

No Drawing. Application May 19, 1943,

5 Claims.

This invention pertains to colloid silver halide emulsions of enhanced speed and contrast. More particularly it pertains tocolloid silver halide emulsions which contain very small amounts of gold and iron salts and to their preparation.

An object of this invention is to provide new sensitized colloid silver halide emulsions. Another object is to provide such emulsions which have good speed and contrast. A further object is to provide such emulsions from readily available inorganic compounds.

Itihas been found that colloid silver halide emulsions which have good speed. and contrast and low fog levels can be made by adding small amountsof water-soluble iron salts, particularly ferric salts such as ferric nitrate, to colloid silver halide emulsions which contain very small amounts of gold or gold and mercury. The emulsions are further sensitized by the addition of a sulfur sensitizer, e. g., sodium thiosulfate, allyl isothiocyanate, thiourea, or an N-substituted thiourea. In the case of gelatin which contains an adequate amount of naturally occurring sulfur compounds, it is not necessary to add a sulfur sensitizer. a

The amount of sulfur sensitizer will vary depending on the chemical constitution of theparticular compound used. In the case of sodium thiosulfate. the amounts may ran e from 1.73 to 9.2 mg. per 765 g. of silver nitrate used in making the emulsion which corresponds to 486 g. of silver based on the element in the final emulsion. Equivalent amounts of other sulfur sensitizers can be used.

The amount of gold and mercury which may be present will vary depending upon the particular salt used. In the case of the preferred salts, chloraurie acid (AuC13-HC1-4H20) is used in an amount of 1.34 to 5.33 mg, and mercuric chloride is used in an amount of 1.32 to 1.97 mg. per 765 g. of .silver nitrate, or based on the silver present in the emulsion, the mol per cents of the two components are re pectively .0000723 to .000288 for gold and .000108 to .000162 for mercury.

It has been found that the amount of iron salts which can be added is not critical. Once the optimum sensitization level is obtained with the gold and'iron or gold, mercury and iron salts, the addition of relatively large quantities of iron salts does not result in a decrease in sensitivity. From 3.0 to 200.0 rugs. and, preferably 3.93 to 3 .44 mgs. of hydrated ferric nitrate, is used per '765 g. of silver nitrate used in making the emulsion. Based on the amount of silver in the emulsion, the amounts are .0002165 to .0110 mol per cent of iron. In the case of other salts. the amounts are, of course, used in chemically equivalent amounts. Suitable additional salts are ferric chloride, ferric sulfate, ferric ammonium sulfate, ferrous nitrate and ferrous chloride.

N-methyl-para-aminophenol sulfate 2.5 Hydroquinone 3.0 Sodium sulfite (anhydrous) 75.0 Borax 5.0 Water to 1.0 liter for nine minutes at 68 F. with the results listed in the following table: [Concentration of solutions: 6X10-5 molar] S Sodium Chl r- Ferric Me? Relaig' Thiosulauric Nitive Fog p fate Acid trate ride Speed ma C0. C0. Cc. Cc.

. pounds.

2 The gold and iron or mixture of gold, iron and mercury are preferably added to the colloid silver halide emulsions after the silver salts have been formed. The washed emulsion -is liquefied and the sulfur sensitizer added if necessary. An aqueous solution of chloraurie acid or of chlorauric acid and mercuric chloride, for example are added in an amount suflicient to introduce the above-prescribed quantities of such com- An aqueous solution of the watersoluble iron salt, e. g., ferric nitrate, is added. The emulsion is then digested for a suitable time to obtain the maximum sensitivity and coated onto a suitable upport to form a thin light-sensitive layer. An optical sensitizing dye, e. g., a cyanine, carbocyanine, merocyanine, pseudocy-- anine, or styryl dye, can be added to the emulsion prior to or subsequent to digestion, if desired.

The invention will be further illustrated but is not intended to be limited by the following examples:

Example I A silver halide dispersion in inert gelatin con-Q taining 5.0% silver iodide and 95.0% silver bromide and a carbocyanine sensitizing dye was di- I vided into samples equivalentto 0.15 mol of silver halide each. Additions as tabulated below were type IB sensitometer, and developed in a developer of the following composition:

Grams The samples described in the above table were 60 aged in an oven maintained at a temperature 3 of 120 F. for one week with the resultsgiven in the resulting tablez;

Emulsion No. gg g Gamma F011 17 40 02 123: 86 10 151; 67, O6 214 69 j 10 246 77 I 12" 214 61 10 238 1 .59 l .14; 123 82 a l3v 15 30 02 14 31. 02.

Example II emulsion ,similar'to, that, of Example I was;-

preparedgand;divided-intoseparate portions. Eerric,nitrate, was added to "one. portion. in' the same. Ferrous quantity as, described. in; Example I. sul ate in an equivalentv quantity on a valence basisswas added to, anotherportion.- The emulsions. were thencoated, exposed and developed asin,E xample I. The-sensitometric results obtained; on testing thefilm, samples are set forth in the following, table:

sensitizing Adjuvaut g Gamma Fog 0304 -a-l 29. 7 FB(N.O3)3 229 74 1O droxy monocarboxylic acids e. g,., lactic or glycolic,

aeids, alkalimetaLSalts of cellulose estersof difl i i y acids, uchasph h i acid, polyvinyl.

alcohol; partially hydrolyzed polyvinyl, acetate and interpolymers thereof with, unsaturated, ma-. terials,such as styrene, maleic acid, etc., watersolublepolyvinyl aeetal's, and; other, hydrophilic.

synthetic or natural resins and polymeric compounds. Suitable hydrophilic colloids of the above types are described in; United; States;.Pa-t;-.

ents; 2, 10, 9 2.2 6.322. 216aza. 364215 and.

The invention moreover is not limited to the specific light-sensitive material described in the,

aboveedetailed examples. On the contrary vari ousother simple andmixed silver. halides may be used as the light-sensitive materials in like manner. Mixtures of silver bromides, chlorides, and/or iodides can be made by adding mixtures of soluble salts of thesehalidesdnlike manner.

advantage of theinvention, is that it pro-.

vides asimple and efiective. method. of; increasingthe speed and contrast ofgphotographic emulsions. A further advantage is that the increase of, speed obtained does not disappear on aging. A still further advantage is that increases in speed and. contrast are attained without increases in fog,

Asmany; widely, different embodiments of the invention.- can.be,= made Without departing from the spirit and scope thereof, it is to be understoodthat'theinvention is not to be limited except as defined by the claims.

What is claimed is:

1. A colloid silver halide emulsion containing water-soluble, gold and iron. alts, in, such pronortio s hatthe. emulsiomcontains .ocuovza. to) 00.02.88 mol; per, cent f gold. and; -Q0.0.216.5.lto.. 0 0) m p t. oi i on bas d, on. he, silver nt; f uch. emuls n...

2-. s et silver halide. mulsion con a nin Water-soluble. g ld and iron s ts. in su h pro..- portions that; the emulsion contains .0800723; ta,

.000288 mol; per, C61 1 f. old and; .0002165 l. p .v nt ron, ba ed. n. the. s lv r. content of such emulsion.

3. A,gelatin silver halide emulsion containing water-soluble gold and iron salts. in such proportions that the emulsion contains, .0000723 to .000288 molper cent of gold; 0002165 to .0110 mol perv cent of iron, and further containing; .0 0027to .00135 mol per cent of a sulfur sensitizer, based on the silver content, of such emulsion,

4, A- gelatin silver halide emulsion containing water-soluble; gold, mercury and iron salts; in; such proportions that theemulsion, contains, .OOD 0 723'to .000288 mol per cent ofgold, .00Q108 to .000162 mol' per cent of mercury, .00 02165 to; .01-10-mol per-centof iron, and further containing .0002? to .00135 v mol per centof sodium thigsulfate, based on; the silver content of such; em-uision,

5. A gelatin silver iodobromide emulsionpre dominating; in silver bromide and containing water-soluble gold; mercury and; iron salts in such proportions that the emulsion contains" .0000'723 to .ooozaa mol-"pen cent of gold, .0001'08:

to= .000162 mol= per cent of mercury,- 1100216510- .0110 mol per cent of iron, and further-contain-- ing--.00027 to .00135 mol percent of sodium thiosulfate; based on thesilver content of such emulsion.

DEWEY BALDSIEFENL' REFERENCE S GITED,

The following references are ofr ecord1in the;

fi e. oi. this patent;

UNITED: STATES. PATENTS:

Number Name Date 2,059,642 Kankelwitz' Nov. 3; 193,6 Waller et al. Apr. 23; 1946] 

1. A COLLOID SILVER HALIDE EMULSION CONTAINING WATER-SOLUBLE GOLD AND IRON SALTS IN SUCH PROPORTIONS THAT THE EMULSION CONTAINS .0000723 TO .000288 MOL PER CENT OF GOLD AND .0002165 TO .0110 MOL PER CENT OF IRON, BASED ON THE SILVER CONTENT OF SUCH EMULSION. 